Our overall objective is to determine the primary site of aldosterone's action on toad urinary bladder epithelial cells by examining the role of transcription and/or translation during hormonal activation of active sodium transport. Specific objective for the total 3 year project are to determine: (1) the role of RNA and protein synthesis during aldosterone-induced active sodium transport across toad bladder epithelial cells; (2) the modifying effect of the precursor pool during aldosterone-stimulated RNA synthesis as measured by H3-uridine-6 tracer; (3) the profile of RNA populations extracted from sub-cellular fractions of toad bladder epithelial cells i.e., nucleoli, nucleoplasm and cytosol and what changes can be identified as being aldosterone induced; (4) if possible, the qualitative identificaiion followeed by isolation and DNA hybridization of a specific aldosterone-induced messenger RNA.